Detailed dosage guidelines and administration information for Allegra (fexofenadine hydrochloride). Includes dose adjustments, warnings and precautions. Medscape - Seasonal allergic rhinitis, chronic idiopathic urticaria-specific dosing for Allegra (fexofenadine), frequency-based adverse effects, comprehensive interactions, contraindications. Overview: Fexofenadine is an antihistamine that is taken to help treat allergy symptoms, such as a runny nose, itchy or watery eyes, sneezing, or an itchy nose or throat. Common side effects may. Allegra (Fexofenadine Hcl) may treat allergy, side effects, dosage, drug interactions, warnings, patient labeling, reviews, and related medications including drug comparison. Allegra (fexofenadine) is a non-drowsy antihistamine used for seasonal allergic rhinitis and chronic idiopathic urticaria. Compared with first-generation agents, it has minimal CNS penetration and is less sedating, making it suitable for daytime use and tasks that require alertness. While some other oral antihistamines may cause you to be drowsy, Allegra® won't. Fexofenadine, the active ingredient in Allegra ®, provides non-drowsy allergy relief with 0% brain interference, relieving allergy symptoms like sneezing, runny nose and itchy eyes. Fexofenadine (Allegra) is an antihistamine that treats and prevents allergy symptoms. It blocks histamine to reduce your symptoms. Want fast, non-drowsy allergy relief? Allegra helps relieve your toughest allergy symptoms, without the drowsy effect, empowering you to live life fully*, everyday. It is a common over-the-counter medication available under many brand names (including Allegra), as well as a generic drug. [11] Therapeutically, fexofenadine is a selective peripheral H 1 blocker. What is Allegra? Allegra (fexofenadine) is an antihistamine used to treat allergy symptoms, including sneezing, itching, watery eyes, and a runny nose in adults and children.